Molting? Did I just screw up?

I adopted a couple of Rouen ducks a couple of weeks ago. The lady whom I got them from said that they were laying eggs but stopped presumably due to the hot weather. I took them in and fed them waterfowl feed, which is basically flock raiser type of feed. I offered oyster shell and grit.

Today I was surprised to see that they are molting. They seemed to be healthy, if still a little skittish. Did I feed incorrectly? Or is this just their time to molt? They're about a year old.

I have Muscovy, Silver Appleyards, Rouens, Black Swedish, Pekins and 2 runners. As well as 1 Silver Appleyard/Khaki Campbell mix. I had thought they were done with the spring molt but they seem to be going through a light molt here lately. ALL of them except the Muscovy.(I have 5 of them) Taking the species into consideration, I have come to the conclusion that it has to do with the heat. The Muscovy being a South American bird and the other 16 being Mallard derivative.
In your case, stress may also be a factor but I wouldn't worry too much. They should settle in just fine.